Tensile tests have been performed on whiskers of iron, copper, and silver 1.2 to 15 μ in diameter. The strongest whiskers which were less than 4 μ in diameter exhibited resolved elastic shear strengths of from two to six percent of their shear moduli. Stress-strain determinations on iron have shown that large deviations from Hooke's law occur beyond two percent strain. As the whiskers increase in size, their strengths decrease with considerable scatter.

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By rapidly reducing the stress after yielding, it was possible to study the plastic deformation of copper and silver whiskers. The whiskers exhibit extremely sharp yield points and extensive easy ``glide'' regions which are due to the propagation of Lüders bands. It is unlikely that the sharp yield points are caused by dislocation pinning. The propagation of the Lüders bands often becomes obstructed giving rise to repeated yielding in the plastic region. The nature of these obstructions and the mechanism of Lüders band propagation are not clear.